The present invention relates to radio receivers and specifically to radio receivers for receiving Radio Data System (RDS) broadcasts.
Radio Data System (RDS) broadcasts are special types of radio broadcasts that are widely implemented in Europe. RDS broadcast transmissions incorporate several types of information in addition to the audio content of the program that is broadcast.
Included in the incorporated information is a PTY (program type display) code. The PTY code is used to inform the listener of the general category of the program of the particular station to which an RDS receiver is tuned. For example, the category might be news, music, drama, educational, scientific, etc.
Another type of information incorporated in RDS signals represents the identity of the specific program being received. The program is identified by program identification codes (PI codes). At a given time, in a given receiving region, a number of broadcasters may be transmitting the same program at different receivable frequencies, each having the same PI code. At a given time different programs with different PI codes, each in the same category and thus having the same PTY code, could be airing simultaneously. RDS broadcasters may also transmit a list, called an AF list, which correlates the freqencies of RDS broadcasters and PI codes of the broadcasts at each frequency.
One feature that can be implemented in an RDS receiver is the PTY function. The PTY function shows, on a display, the category of the program being received. The display permits the user to select a station based on the general program content.
The additional equipment in RDS receivers for performing the PTY function serves no special purpose at times when no program in the selected category is broadcasting. For example, such recievers require a key switch for the PTY function. This requirement increases the number of keys and thereby the difficulty of operation.